Development device

ABSTRACT

A development device of this invention includes a developer carrier for transporting a developer to a development region opposite to an image bearing body as binding the developer thereto by means of a magnetic force, and a regulating member opposing the developer carrier across a required distance therebetween and regulating the amount of developer transported by the developer carrier to the development region, the regulating member having a greater roughness at its surface opposite to the developer carrier than the developer carrier.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a development device for usein image forming apparatuses, such as copying machines, printers and thelike, which is adapted to develop an electrostatic latent image formedon an image bearing body and more particularly, to a development devicecomprising a developer carrier for transporting a developer to adevelopment region opposite to the image bearing body as binding thedeveloper thereto by means of a magnetic force, and a regulating memberfor regulating the amount of developer carried on the developer carrierto the development region, the regulating member opposing the developercarrier across a required distance therebetween.

2. Description of the Related Art

Various types of development devices have conventionally been used inthe image forming apparatuses, such as copiers, printers and the like,for developing an electrostatic latent image formed on the image bearingbody.

As shown in FIG. 1, an example of such development devices comprises acylindrical developer sleeve 11 (developer carrier) opposing an imagebearing body 1 and including a magnet member 12 with a plurality ofmagnetic poles, N, S, . . . , on the inner periphery thereof. Thedeveloper sleeve 11 is adapted to rotate to carry the developer towardan image bearing body 1 as binding the developer thereto by means of amagnetic force of the magnet member 12, while a regulating member 13opposing the developer sleeve 11 across a required distance Dbtherebetween serves to regulate the amount of developer thus carried onthe developer sleeve 11 thereby allowing the developer sleeve 11 totransport a regulated amount of developer to a development regionopposite to the image bearing body 1 for development of an electrostaticlatent image formed on the image bearing body 1.

The aforesaid development device known to the art is arranged such thata somewhat great distance Db is defined between the developer sleeve 11and the regulating member 13 so that the developer in the form of amagnetic brush is introduced into the development region opposite to theimage bearing body 1, coming into contact with the image bearing body 1for development of the electrostatic latent image formed thereon.

Unfortunately, however, in the development process performed by bringingthe magnetic brush into contact with the image bearing body 1, themagnetic brush may scrape off a toner supplied to the image bearing body1, thus producing a streak-like noise or disturbance in a resultantimage.

Hence, a recent study has been made on an arrangement wherein adecreased distance Db is defined between the developer sleeve 11 and theregulating member 13 for reduction in the amount of developer carried onthe developer sleeve 11 to the development region where theelectrostatic latent image is developed with the developer kept fromcontact with the image bearing body 1.

Unfortunately, a problem exists with the decreased distance Db betweenthe developer sleeve 11 and the regulating member 13. More specifically,there may occur variations of the amount of developer transported by thedeveloper sleeve 11 to the development region or a gap between thedeveloper sleeve 11 and the regulating member 13 may become clogged witha foreign matter having entered the development device or an agglomerateof the developer and the like formed within the development device, theclogged gap hindering the developer sleeve 11 from carrying thedeveloper thereon. This results in the production of a white area, suchas a white streak, in the resultant image.

As a solution to this problem, there has been offered a developmentdevice wherein the regulating member 13 is formed of a magnetic materialso as to magnetically bind the developer thereto, thus allowing thedeveloper sleeve 11 to transport a constant, small amount of developerto the development region opposite to the image bearing body 1 despite agreat distance Db defined between the developer sleeve 11 and theregulating member 13.

Recently, however, the developer sleeve 11 is required to transport afurther decreased amount of developer to the development region forproduction of high-definition images with an enhanced developmentefficiency.

Hence, even the development device with the regulating member formed ofthe magnetic material must define a reduced distance Db between thedeveloper sleeve 11 and the regulating member 13. Therefore, there stillexists the aforementioned problem that varied amounts of developer aretransported by the developer sleeve 11 to the development region or thegap between the developer sleeve 11 and the regulating member 13 becomesclogged with the foreign matter having entered the device or theagglomerate of the developer and the like formed within the device. Theclogged gap hinders the developer sleeve 11 from carrying thereon thedeveloper, resulting in the production of a white area, such as a whitestreak, in the resultant image.

SUMMARY OF THE INVENTION

It is therefore, an object of the invention to provide a developmentdevice wherein the regulating member, as magnetically binding thedeveloper thereto, regulates the amount of developer transported by thedeveloper carrier to the development region opposite to the imagebearing body and the developer carrier is allowed to transport a smallamount of developer to the development region despite an increaseddistance defined between the developer carrier and the regulating memberin opposed relation.

It is another object of the invention to provide a development deviceadapted for prevention of the variations in the amount of developertransported to the development region by means of the developer carrieradapted to carry thereon a reduced amount of developer.

It is still another object of the invention to provide a developmentdevice adapted to prevent the gap between the regulating member and thedeveloper carrier from becoming clogged with a foreign matter havingentered the development device or an agglomerate of the developer andthe like formed within the device, thereby avoiding the production of awhite area, such as a white streak, in the resultant image.

It is yet another object of the invention to provide a developmentdevice allowing the developer carrier to transport a constant, smallamount of developer to the development region for a reliable productionof favorable, high-definition images.

The development device according to the invention comprises a developercarrier for transporting a developer to the development region oppositeto an image bearing body while binding the developer thereto by means ofa magnetic force, and a regulating member opposing the developer carrieracross a required distance therebetween and regulating the amount ofdeveloper transported by the developer carrier to the developmentregion, the regulating member having a greater roughness at its surfaceopposite to the developer carrier than the developer carrier.

In the development device of this invention, a frictional force isproduced between the developer and the developer-carrier-opposed surfaceof the regulating member when the developer, as magnetically bound tothe developer carrier, is carried through a gap between the regulatingmember and the developer carrier in opposed relation.

With the arrangement of the invention wherein the regulating member hasa greater surface roughness at its developer-carrier-opposed surfacethan that of the developer carrier in opposed relation, an increasedfrictional force is produced between the carrier-opposed surface of theregulating member and the developer, thus hindering the developer frombeing passed through the gap between the regulating member and thedeveloper carrier. This provides for a reliable transportation of aconstant, small amount of developer to the development region despite agreat distance defined between the regulating member and the developercarrier.

Additionally, such a great distance defined between the regulatingmember and the developer carrier is effective to prevent the gap betweenthe developer carrier and the regulating member from becoming cloggedwith the foreign matter and the like and hence, a reliable production offavorable images free from a white area, such as a white streak, isassured.

These and other objects, advantages and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings which illustrate specificembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial diagrammatic view for illustrating a developmentdevice wherein a regulating member regulates the amount of developercarried on a developer sleeve while the developer is transported by thedeveloper sleeve to a development region opposite to an image bearingbody;

FIG. 2 is a partial diagrammatic view for illustrating a state whereinthe developer carried on the developer sleeve is regulated by theregulating member;

FIG. 3 is a graphical representation of Examples 1 to 3 for illustratingindividual relationships between the distance Db from the regulatingmember to the developer sleeve and the amount of developer transportedto the development region by means of the developer sleeve;

FIG. 4 is a graphical representation of Examples 4 to 6 for illustratingindividual relationships between the distance Db from the regulatingmember to the developer sleeve and the amount of developer transportedto the development region by means of the developer sleeve; and

FIG. 5 is a diagrammatic view for illustrating Examples 7 to 12 whereina piece of Mylar is attached to the regulating member in contactrelation with the developer sleeve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, description will hereinbelow be given on preferred embodiments ofthe development device according to the invention.

According to an aspect of the development device of the invention, inorder that the regulating member serves to regulate the amount ofdeveloper transported by the developer carrier to the development regionin the aforementioned manner, the regulating member has a greatersurface roughness at its developer-carrier-opposed surface than thedeveloper carrier and is formed of a magnetic material. With thisconstruction, when carried through the gap defined between theregulating member and the developer carrier in opposed relation, thedeveloper is not only regulated by the frictional force produced betweenthe developer and the carrier-opposed surface of the regulating memberbut is also magnetically bound to the regulating member.

This provides for a proper regulation of the amount of developer carriedon the developer carrier to the development region despite an increaseddistance defined between the developer carrier and the regulatingmember. Thus are reduced the variations of the amount of developertransported to the development region while the gap between thedeveloper carrier and the regulating member is prevented from becomingclogged with a foreign matter and the like having entered thedevelopment device. As a result, a reliable production of favorableimages free from a white area, such as a white streak, is assured.

Incidentally, the roughness may be imparted to the carrier-opposedsurface of the regulating member by means of cutting or the like.

According to another aspect of the development device of the invention,in order that the aforesaid regulating member regulates the amount ofdeveloper carried on the developer carrier for transportation of aconstant, small amount of developer, the developer carrier preferablyhas a 10-point average roughness Rs of not greater than 30 μm at itssurface and the relationship between the 10-point average roughness Rsof the surface of the developer carrier and that Rb of thecarrier-opposed surface of the regulating member preferably satisfies1.1≦Rb/Rs≦5.0.

Further, in order that the carrier-opposed surface of the regulatingmember exerts a sufficient frictional force on the developer therebyregulating the amount of developer carried through the gap between theregulating member and the developer carrier as a part of theaforementioned regulation of the amount of developer carried on thedeveloper carrier, the carrier-opposed surface of the regulating memberpreferably has a thickness of not smaller than 0.5 mm with respect tothe moving direction of the developer.

According to a still another aspect of the development device of theinvention, in order to allow the regulating member to positivelyregulate the amount of developer passed through the gap between theregulating member and the developer carrier when a developer comprisinga carrier and a toner is used, the carrier preferably has an averageparticle size of 20 to 70 μm.

Next, the development device according to a preferred embodiment of theinvention will be described in detail with reference to the accompanyingdrawings.

Similarly to the prior-art development device shown in FIG. 1, thedevelopment device of this embodiment comprises a cylindrical developersleeve 11 (developer carrier) opposing an image bearing body 1 andincluding a magnet member 12 with a plurality of magnetic poles, N, S, .. . , on the inner periphery thereof. The developer sleeve 11 is adaptedto rotate for transportation of a developer 2 toward the image bearingbody 1 as binding the developer thereto by means of a magnetic force ofthe magnet member 12.

On the other hand, a regulating member 13 opposing the developer sleeve11 across a required distance Db therebetween serves to regulate theamount of developer 2 thus carried on the developer sleeve 11 so thatthe image bearing body 1 may be supplied with a regulated amount ofdeveloper. Thus, a proper amount of developer is transported by thedeveloper sleeve 11 to a development region opposite to the imagebearing body 1 for development of an electrostatic latent image formedon the image bearing body 1.

In the development device of this embodiment, the aforesaid regulatingmember 13 is formed of a magnetic material and has its surface 13aopposite to the developer sleeve 11 finished by cutting so as to beimparted with a greater surface roughness than that of the developersleeve 11, as shown in FIG. 2.

With this construction, the developer 2 carried through a gap betweenthe developer sleeve 11 and the regulating member 13 is magneticallybound to the regulating member 13 while an increased frictional force isproduced between the sleeve-opposed surface 13a of the regulating member13 and the developer 2, hindering the developer 2 from being carriedthrough the gap between the regulating member 13 and the developersleeve 11. This provides for a reliable transportation of a constant,small amount of developer 2 to the development region in oppositerelation to the image bearing body 1 despite an increased distance Dbdefined between the regulating member 13 and the developer sleeve 11.

Next, advantages of the development device according to the inventionwill be clarified by way of various examples thereof.

(EXAMPLES 1 to 3)

In these examples, a developer comprising a mixture of a carrier with anaverage particle size of 30 μm and a toner with an average particle sizeof 8 μm and having a toner concentration of 15 wt % was used in thedevelopment device of the above construction. A developer sleeve 11 usedtherein had an outside diameter of 24.5 mm and a 10-point averageroughness Rs of 10.0 μm at its surface, which was subject to asandblasted finish.

On the other hand, there were used three types of regulating members 13,each of which was formed of a magnetic material of SUS430 and had athickness t of 1.5 mm with respect to the moving direction of thedeveloper. The regulating members of Examples 1 to 3 had 10-pointaverage roughnesses Rb of 2.0 μm, 10.0 μm, and 15.0 μm at thesleeve-opposed surfaces 13a thereof, respectively. The relationshipsbetween the 10-point average roughness Rs of the surface of thedeveloper sleeve 11 and the 10-point roughnesses Rb of thesleeve-opposed surfaces 13a of the regulating members 13 of Examples 1to 3, or Rb/Rs values were at 0.2, 1.0 and 1.5, respectively.

The aforesaid developer sleeve 11 was rotated at a speed of 265 mm/secwhile the amount of developer carried on the developer sleeve 11 wasregulated by each regulating member 13. Measurement was taken on theamount of developer carried past each regulating member 13 by means ofthe developer sleeve 11, with the distance Db varied between eachregulating member 13 and the developer sleeve 11. The results are shownin FIG. 3.

As apparent from the results, in the development device of Example 3wherein the sleeve-opposed surface 13a of the regulating member has agreater 10-point average roughness Rb than that Rs of the surface of thedeveloper sleeve 11 and the Rb/Rs value is 1.5, smaller amounts ofdeveloper are transported than in the development devices of Example 1with the Rb/Rs value of 0.2 and of Example 2 with the Rb/Rs value of 1.0even when the distance Db between the developer sleeve 11 and theregulating member 13 is increased. Additionally, the device of Example 1presents reduced changes in the amount of developer carried past theregulating member 13 despite the varied distances Db defined between thedeveloper sleeve 11 and the regulating member 13, thus achieving astable transportation of small amounts of developer to the developmentregion by means of the developer sleeve 11.

(EXAMPLES 4 to 6)

In these examples, the same developer as in the aforementioned exampleswas used whereas the regulating member 13 was formed of the magneticmaterial of SUS430 and had a thickness t of 1.5 mm with respect to themoving direction of the developer. The sleeve-opposed surface 13a of theregulating member 13 had a 10-point average roughness Rb of 10.0 μm.

On the other hand, there were used three types of developer sleeves 11,each of which had an outside diameter of 24.5 mm. The developer sleevesof Examples 4 to 6 had 10-point average roughnesses Rs of 30.0 μm, 10.0μm and 2.0 μm at the surfaces thereof, respectively. The relationshipsbetween the 10-point average roughnesses Rs of the surfaces of thedeveloper sleeves 11 and that Rb of the sleeve-opposed surface 13a ofthe regulating member 13, or the Rb/Rs values were at 0.3 in Example 4,at 1.0 in Example 5 and at 5.0 in Example 6.

Each of the aforesaid developer sleeves 11 was rotated at a speed of 265mm/sec while the amount of developer carried on each developer sleeve 11was regulated by the aforesaid regulating member 13. Measurement wastaken on the amount of developer carried past the regulating member 13by means of the developer sleeve 11, with the distance Db varied betweeneach developer sleeve 11 and the regulating member 13. The results areshown in FIG. 4.

As apparent from the results, in the development device of Example 6wherein the sleeve-opposed surface 13a of the regulating member 13 has agreater 10-point average roughness Rb than that Rs of the surface of thedeveloper sleeve 11 and the Rb/Rs value is 0.2, smaller amounts ofdeveloper are transported than in the devices of Example 4 with theRb/Rs value of 0.2 and of Example 5 with the Rb/Rs value of 1.0 evenwhen the distance Db between the developer sleeve 11 and the regulatingmember 13 is increased. Additionally, the device of Example 6 presentsreduced changes in the amount of developer carried past the regulatingmember 13 despite the varied distances Db defined between the developersleeve 11 and the regulating member 13, thus achieving a stabletransportation of small amounts of developer to the development regionby means of the developer sleeve 11.

(EXAMPLES 7 to 12)

In these examples, the same developer as in the aforementioned exampleswas used in the above development device. Developer sleeves 11 usedtherein had an outside diameter of 24.5 mm and a 10-point averageroughness Rs of 2 μm, 6 μm, 10 μm or 30 μm at their surfaces. On theother hand, regulating members 13 were each formed of the magneticmaterial of SUS430 and had a thickness t of 1.5 mm with respect to themoving direction of the developer. The sleeve-opposed surface 13a ofeach regulating member 13 had a 10-point average roughness Rb of 2 μm,10 μm or 15 μm.

Each of the aforementioned developer sleeves 11 and each of theregulating members 13 were used in combination as shown in the followingTable 1. The Rb/Rs values of the respective examples are also shown inthe table.

Each of the developer sleeves 11 was rotated at a speed of 265 mm/secwhile the distance Db between the developer sleeve 11 and the regulatingmember 13 was adjusted so as to allow the regulating member 13 toregulate the amount of developer carried past the regulating member 13to 5.0 mg/cm², the developer being carried on the developer sleeve 11.There were examined variations of the amount of developer carried pastthe regulating member 13 by means of each developer sleeve 11. Theresults are shown in Table 1.

As shown in FIG. 5, a piece of Mylar 3, which is 2 mm in width and 0.18mm in thickness, was attached to each regulating member 13 at itsupstream-side surface 13b with respect to the moving direction of thedeveloper in contact relation with the developer sleeve 11, therebyintentionally creating a state wherein a clogging is caused by theforeign matter. Then, the occurrence of white streaks on the surface ofeach developer sleeve 11 was examined. The results are shown in Table 1.

As to the varied transportation of the developer, the state of thedeveloper on the surface of each developer sleeve 11 was visuallyinspected and rated on ◯-to-X scale. That is, a heavily variedtransportation of developer resulting in an image with heavy noise wasgiven "X"; a varied transportation of the developer resulting in animage with recognizable noise was given "Δ"; and a constanttransportation of the developer achieving a noiseless image was given"◯".

                  TABLE 1                                                         ______________________________________                                        Example Rs (μm)                                                                            Rb (μm)                                                                             Rb/Rs Db (mm) V.T. W.S.                              ______________________________________                                        7       10      10       1.0   0.4     Δ                                                                            X                                 8       10      2        0.2   ≦0.1                                                                           X    X                                 9       10      15       1.5   0.7     ◯                                                                      ◯                     10      6       10       1.7   0.6     ◯                                                                      ◯                     11      30      10       0.3   ≦0.1                                                                           X    X                                 12      2       10       5.0   0.8     ◯                                                                      ◯                     ______________________________________                                         Note: In the table, "V.T." denotes "varied transportation of the              developer" and "W.S." denotes "white streak".                            

As apparent from the results, in Examples 9, 10 and 12 wherein thesleeve-opposed surfaces 13a of the regulating members 13 have greaterroughnesses than the surfaces of the developer sleeves 11, increaseddistances Db may be defined between the developer sleeves 11 and theregulating members 13 to allow the regulating members 13 to regulate theamount of developer on the developer sleeves 11 to 5.0 mg/cm². Inaddition, the variations of the amount of developer carried on thedeveloper sleeves 11 are prevented. Furthermore, these developer sleevesdo not suffer the occurrence of white streaks thereon when the cloggingis intentionally caused by the foreign matter and thus, a stableproduction of favorable images is assured.

(EXAMPLES 13 to 18)

In these examples, too, the same developer as in the aforementionedexamples was used in the above development device. A developer sleeve 11used therein had an outside diameter of 24.5 mm and a 10-point averageroughness Rs of 15 μm at the surface thereof. On the other hand,regulating members 13 used therein were each formed of the magneticmaterial of SUS430 and had a 10-point average roughnesses Rb of 10 μm or15 μm at their sleeve-opposed surfaces 13a. The Rb/Rs value was set at1.0 or 1.5. Each regulating member 13 had a thickness t with respect tothe moving direction of the developer as shown in the following Table 2.

Then, the developer sleeve 11 was rotate d at a speed of 265 mm/secwhile the distance Db between the developer sleeve 11 and eachregulating member 13 was adjusted so as to allow the regulating member13 to regulate the amount of developer carried past the regulatingmember 13 to 5.0 mg/cm², the developer being carried on the developersleeve 11. Similarly to Examples 7 to 12, there were examined variationsof the amount of developer carried past the regulating member 13 bymeans of the developer sleeve 11. The results are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                        Example   Rb/Rs   t (mm)     Db (mm)                                                                              V.T.                                      ______________________________________                                        13        1.5     0.5        0.4    ◯-Δ                     14        1.5     1.0        0.6    ◯                             15        1.5     1.5        0.7    ◯                             16        1.5     2.0        0.75   ◯                             17        1.5     2.5        1.0    ◯                             18        1.0     0.5        0.25   X                                         ______________________________________                                    

As apparent from the results, in Examples 13 to 17 wherein thesleeve-opposed surfaces 13a of the regulating members 13 have greaterroughnesses than the surface of the developer sleeve 11, increaseddistances Db may be defined between the developer sleeve 11 and theregulating members 13 to allow the regulating members 13 to regulate theamount of developer on the developer sleeve 11 to 5.0 mg/cm². Inaddition, the variations of the amount of developer carried on thedeveloper sleeve 11 are reduced. Particularly, the increased thickness tof the regulating member 13 with respect to the moving direction of thedeveloper allows for further increase in the distance Db between thedeveloper sleeve 11 and the regulating member 13 whereby the developersleeve 11 can transport a small amount of developer to the developmentregion in a stable manner.

(EXAMPLES 19 to 23)

In these examples, used in the aforementioned development device was adeveloper sleeve 11 having an outside diameter of 24.5 mm and a 10-pointaverage roughness Rs of 10 μm at the surface thereof. On the other hand,a regulating member 13 was formed of the magnetic material of SUS430,and had a thickness t of 1.5 mm with respect to the moving direction ofthe developer and a 10-point average roughness Rb of 15 μm at itssleeve-opposed surface 13b. The Rb/Rs value was at 1.5.

Five types of carriers with average particle sizes (P.S.) of 15 μm, 20μm, 40 μm, 50 μm and 70 μm were blended with toner particles with anaverage particle size of 8 μm, respectively, and thus were prepareddevelopers having a toner concentration of 15 wt%.

In each example, the aforementioned developer sleeve 11 was rotated at aspeed of 265 mm/sec while the distance Db between the developer sleeve11 and the regulating member 13 was adjusted so as to allow theregulating member 13 to regulate the amount of developer carried pastthe regulating member to 5.0 mg/cm², the developer being carried on thedeveloper sleeve 11. Similarly to Examples 7 to 12, there were examinedvariations (V.T.) of the amount of developer carried past the regulatingmember 13 by means of the developer sleeve 11. The results are shown thefollowing Table 3.

                  TABLE 3                                                         ______________________________________                                        Example  Rb/Rs   Carrier P.S. (μm)                                                                        Db (mm)                                                                              V.T.                                    ______________________________________                                        19       1.5     15            0.3    X-Δ                               20       1.5     20            0.5    ◯                           21       1.5     40            0.7    ◯                           22       1.5     50            0.7    ◯                           23       1.5     70            0.8    ◯                           ______________________________________                                    

As apparent from the results, the greater particle size of the carrierused in the developer allows for the corresponding increase in thedistance Db between the regulating member 13 and the developer sleeve 11whereby a stable transportation of a small amount of developer isassured. The developer including the carrier not smaller that 20 μm inparticle size, in particular, do not result in the variations of themount of developer transported.

Although the present invention has been fully described by way ofexample, it is to be noted that various changes and modification will beapparent to those skilled in the art.

Therefore, unless otherwise such changes and modifications depart fromthe scope of the present invention, they should be construed as beingincluded therein.

What is claimed is:
 1. A development device comprising:a developercarrier member for transporting a developer to a development regionopposite to an image bearing body by binding the developer to thedeveloper carrier member by means of a magnetic force, said developercomprising a toner and a carrier, and a regulating member opposing thedeveloper carrier member across a required distance therebetween andregulating the amount of developer transported by the developer carriermember to the development region, said regulating member being formed ofa magnetic material and having a greater roughness at a surface oppositeto the developer carrier member than the developer carrier member.
 2. Adevelopment device of claim 1, wherein said surface of said regulatingmember is a cut surface.
 3. A development device of claim 1, whereinsaid developer carrier member has a surface roughness Rs of not greaterthan 30 μm, and a relationship between the surface roughness Rs of thedeveloper carrier member and a surface roughness Rb of said surface ofthe regulating member satisfies 1.1≦Rb/Rs≦5.0.
 4. A development deviceof claim 1, wherein said regulating member has a thickness of notsmaller than 0.5 mm at an end portion of said regulating member havingsaid surface.
 5. A development device of claim 1, wherein said carrierhas an average particle size ranging from 20 to 70 μm.
 6. A developmentdevice comprising:a developer carrier member for transporting adeveloper to a development region opposite to an image bearing body bybinding the developer to the developer carrier member by means of amagnetic force, said developer comprising a toner and a carrier, and aregulating member opposing the developer carrier member across arequired distance therebetween and regulating the amount of developertransported by the developer carrier member to the development region,said regulating member being formed of a magnetic material, wherein anincreased frictional force is produced between a surface of saidregulating member opposing said developer carrier member and thedeveloper.
 7. A development device of claim 6, wherein said regulatingmember has a thickness of not smaller than 0.5 mm at an end portion ofsaid regulating member having said surface.
 8. A development device ofclaim 6, wherein said carrier has an average particle size ranging from20 to 70 μm.
 9. A development device comprising:a developer carrier fortransporting a developer to a development region opposite to an imagebearing body as binding the developer thereto by means of a magneticforce, and a regulating member opposing the developer carrier across arequired distance therebetween and regulating the amount of developertransported by the developer carrier to the development region, whereinsaid developer carrier has a surface roughness Rs of not greater than 30μm and a relationship between the surface roughness Rs of the developercarrier and a surface roughness Rb of a developer-carrier-opposedsurface of said regulating member satisfies 1.1≦Rb/Rs≦5.0.
 10. Adevelopment device of claim 9, wherein said regulating member is formedof a magnetic material.
 11. A development device of claim 9, whereinsaid regulating member has a thickness of not smaller than 0.5 mm at itsdeveloper-carrier-opposed surface.
 12. A development device of claim 9,wherein said developer comprises a toner and a carrier.
 13. Adevelopment device of claim 12, wherein said carrier has an averageparticle size ranging from 20 to 70 μm.